This application is based on and claims priority from Japanese Application No. HEI 3-205002 filed May 13, 1991, the disclosure of which is incorporated herein by reference.
The present invention relates to a method for measuring performance characteristics of a lens to be used at an operating wavelength, by passing a light with a wavelength different from the operating wavelength through the lens.
Measurements for testing the performance of a lens are desirably obtained in an environment that is either identical or close to an actual environment in which the lens of interest is to be used. Therefore, when measuring lens performance it is preferred that a light source be used which emits rays of light at a wavelength similar to the operating wavelength.
Conventional lenses are sometimes adapted to be operated at wavelengths outside the visible range. If the performance of such a conventional lens is measured using an operating wavelength which is outside the visible range, the quality of the measurement resulting is undesirably poor. Accordingly, it is necessary to perform a measurement using a light source that emits at a wavelength in the visible range which is different from the operating wavelength. However, if the performance of the conventional lens is measured using a light source that emits at a wavelength which differs greatly from the operating wavelength, errors in measurement may occur from spherical aberrations which occur at the nonoperating wavelength.